1. Field of the Invention
The present invention relates to a light emitting device and a method of manufacturing the same, and more particularly, to a gallium nitride (hereinafter, referred to as “GaN”)-based light emitting device (LED) having a vertical-type structure and a method of manufacturing the same.
2. Discussion of the Background
Recently, as light emitting devices having GaN semiconductors are widely expected to replace typical light sources including incandescent lamps, fluorescent lamps, and mercury arc lamps, researches are being actively conducted into high-power GaN-based light emitting devices.
To manufacture such a GaN-based light emitting device, generally, an n-type GaN layer, an undoped InGaN layer, and a p-type GaN layer are sequentially stacked over a nonconductive sapphire substrate, and electrodes are formed over the n-type GaN layer and the p-type GaN layer, respectively. Since the sapphire substrate is nonconductive, the light emitting device typically has a horizontal-type structure. That is, the electrodes respectively formed over the n-type GaN layer and the p-type GaN layer are horizontally disposed. Thus, current spreading-resistance is great in a high-power operation, decreasing optical power. Also, since heat produced in a device operation is not effectively released through the sapphire substrate, there is a limitation that thermal stability of the device is degraded, thereby making a problem in the high-power operation.
To address these limitations and realize high-power GaN-based light emitting devices, flip-chip-type light emitting devices using a flip-chip package have been proposed. In such a flip-chip-type light emitting device, an electrode of a vertical-type light emitting device is connected to a heat sink through a solder. Since, in the flip-chip-type light emitting device, light emits from an active layer to the outside through a sapphire substrate, a thick p-type ohmic electrode is applicable instead of a transparent electrode, thus reducing the current spreading-resistance. However, the flip-chip-type package used for the flip-chip-type light emitting device causes a manufacturing process to be complicated. Moreover, optical efficiency characteristics of the flip-chip-type light emitting device are degraded because a large amount of photons are absorbed into the sapphire substrate while the light emits from the active layer to the outside through the sapphire substrate.